1. Field of the Invention
The present invention relates to a vibration isolating apparatus for suppressing vibration transmitted from a vibration generating portion such as an engine or the like to a vibration receiving portion such as a vehicle body or the like, which is applicable to automobiles, construction machinery, general industrial machinery, and the like.
2. Description of the Related Art
A vibration isolating apparatus is provided between the engine of a vehicle which is a vibration generating portion and the vehicle body which is a vibration receiving portion. The vibration isolating apparatus is constructed so as to absorb vibration generated by the engine and thereby suppress the amount of vibration transmitted to the vehicle body. Vibration from the engine can here generally be considered to be a compound of pitch, which is vibration substantially in the vertical direction, and roll, which is vibration substantially in the horizontal direction. The amplitude and frequency of both the pitch and roll change according to the number of engine revolutions, the size of the engine load, and the like. Moreover, the amplitude and frequency of the vibration transmitted from the engine change according to changes in the number of engine revolutions, namely, according to changes in the vehicle running speed. Specifically, when a vehicle is travelling at between 70-80 km/h, shaking vibration in a comparatively low frequency range (less than 15 Hz) is generated. Alternatively, when the vehicle is idling or is travelling at less than 5 km/h, idling vibration in a comparatively high frequency range (20-40 Hz) is generated. Therefore, when considering the vibration absorbing performance of a vibration isolating apparatus, when shaking vibration is being generated, a high spring constant relative to the input vibration is able to effectively absorb the shaking vibration. When idling vibration is being generated, a low spring constant relative to the input vibration is able to effectively absorb the idling vibration.
Known examples of vibration isolating apparatuses used as engine mounts include hydraulic types having a rubber elastic body, a pressure receiving fluid compartment, and a plurality of fluid sub-compartments in which the pressure receiving fluid compartment and fluid sub-compartments are connected to each other by restricting passages each having a different length and cross-sectional area. In this type of vibration isolating apparatus, the aims are that vibration be absorbed by the fluid resonance and the like of the fluid present in the restricting passage and to reduce the dynamic spring constant (dynamic stiffness) relative to the vibration in each frequency range by switching which fluid sub-compartment is connected to the pressure receiving fluid compartment according to the frequency range of the input vibration.
However, in a hydraulic-type vibration isolating apparatus, when the fluid sub-compartment connected to the pressure receiving fluid compartment is switched according to the frequency range of the input vibration, it is possible to effectively reduce the dynamic spring constant relative to the pitch acting mainly as a vertical load on the elastic body. However, has not been possible to sufficiently reduce the dynamic spring constant relative to the roll acting mainly as a shear load on the elastic body. Therefore, in a hydraulic type vibration isolating apparatus, normally the static spring constant in the direction of the shear load of the elastic body is set at a somewhat high level so that the shaking vibration can be effectively absorbed. Because of this, when conventional hydraulic vibration isolating apparatuses have been used as engine mounts, they have not always been able to sufficiently absorb the roll when idling vibration is generated.
In consideration of the above, the aim of the present invention is to provide a vibration isolating apparatus capable of adjusting both a static spring constant relative to the vertical load of an elastic body and a static spring constant relative to the shear load of the elastic body to suitable values according to the characteristics of the input vibration.
The first aspect of the present invention is a vibration isolating apparatus comprising: a first mounting member connected to one of a vibration generating portion and a vibration receiving portion; a second mounting member connected to the other one of the vibration generating portion and the vibration receiving portion; an elastic body capable of elastic deformation which is provided between the first mounting member and the second mounting member; an intermediate plate for partitioning the elastic body into a first elastic piece and a second elastic piece cross-sectionally relative to a vertical load from the first mounting member or second mounting member; and restraining means provided together with the first elastic piece between the first mounting member and the intermediate plate, which restrains movement of the intermediate plate relative to the first mounting means when operated, and allows movement of the intermediate plate relative to the first mounting means when not operated.
According to this vibration isolating apparatus, an intermediate plate partitions an elastic body into a first elastic piece and a second elastic piece cross-sectionally relative to a vertical load applied from a first mounting member or a second mounting member. The restraining means prevents movement of the intermediate plate relative to the first mounting member when operated, and allows movement of the intermediate plate relative to the first mounting means when not operated. Thus elastic deformation of the first elastic piece is prevented when the restraining means is operated, and elastic deformation of the first elastic piece caused by the load transmitted from the first mounting member or the second mounting member is allowed when the restraining means is operated.
As a result, when the restraining means is operated, only the second elastic piece is able to elastically deform and function as a main absorption body. Therefore, the static spring constants of the elastic body relative to the vertical load and shear load transmitted from the first mounting member or the second mounting member are each able to be made larger than when the restricting means is not being operated. Moreover, when the restraining means is not operated, both the first elastic piece and the second elastic piece become elastically deformable and function as two main absorption bodies arranged serially to each other. Therefore, the static spring constants of the elastic body relative to the vertical load and shear load transmitted from the first mounting member or the second mounting member are each able to be made smaller than when the restraining means is being operated.
The term xe2x80x9cvertical loadxe2x80x9d used here refers to a load which generates a deformation by compressing an elastic body or a deformation by stretching the elastic body. The term xe2x80x9cshear loadxe2x80x9d used here refers to a load which generates shear stress relative to the vertical load in the first elastic piece and second elastic piece.
The second aspect of the vibration isolating apparatus of the present invention is a vibration isolating apparatus according to the first aspect of the present invention further having a pressure receiving fluid compartment provided between the second mounting member and the intermediate plate, at least a portion of the interior wall of the pressure receiving fluid compartment being formed by the second elastic piece, wherein the content volume of the pressure receiving fluid compartment is changed by elastic deformation of the second elastic piece, the vibration isolating apparatus also having a fluid sub-compartment connected to the pressure receiving fluid compartment by a restricting passage.
According to this vibration isolating device, the pressure receiving fluid chamber is made to expand and contract by the deformation of the second elastic piece. Moreover, the fluid in the pressure receiving fluid compartment and the fluid sub-compartment travels reciprocally between the two compartments via the restricting passage. Accordingly, vibration isolation can be improved by the vibration damping action arising from changes in the pressure of the fluid, viscous resistance to the fluid flow, the fluid resonance, and the like generated by the through holes.
The third aspect of the vibration isolating means of the present invention is a vibration isolating apparatus according to the first or second aspects of the present invention, wherein the restraining means has an electromagnet which is fixed to one of the first mounting member and the intermediate plate and, when drive current is supplied to the electromagnet, the electromagnet attracts the other one of the first mounting member and intermediate plate which are formed from a magnetic substance.
According to the this vibration isolating apparatus, an electro magnet is fixed to one of the first mounting member and the intermediate plate, and drive current is supplied to this electromagnet. This causes the other one of the first mounting member and the intermediate plate to be attracted to the electromagnet by the magnetic force from the electromagnet. As a result, when drive current is supplied, the intermediate plate can be prevented from moving relatively to the first mounting member. Moreover, when the supply of drive current is halted, the intermediate plate is released from its state of being restrained by the electromagnet and is able to move relatively to the first mounting member.
The fourth aspect of the vibration isolating apparatus of the present invention is a vibration isolating apparatus according to any of the first through third aspects of the present invention, wherein the restraining means is fixed to one of the first mounting member and the intermediate plate, and is press-contacted to the other one of the first mounting member and the intermediate plate when in operation and separated from the other one of the first mounting member and the intermediate plate when not in operation so as to form a clearance larger than the amplitude of the idling vibration of the vehicle.
According to this vibration isolating apparatus, the restraining means which is fixed to one of the first mounting member and the intermediate plate is press-contacted to the other of the first mounting member and intermediate plate when in operation. Consequently, when in operation, because the intermediate plate is fastened to the first mounting member by the connection with the restraining means, the intermediate plate can be prevented from moving relatively to the first mounting member.
Furthermore, because the restraining means forms a clearance larger than the amplitude of the idling vibration when separated from the other one of the first mounting member and the intermediate plate when the restraining means is not in operation, the intermediate plate is released from its state of being restrained by the restraining means so as to become able to move relatively to the first mounting member. At the same time, the restraining means does not interfere with (touch the top of) the intermediate plate even when idling vibration is input into the first mounting member.
The fifth aspect of the vibration isolating apparatus of the present invention is a vibration isolating apparatus according to any of the first to fourth aspects of the present invention, wherein the first elastic piece is a rubber elastic body.
According to this vibration isolating apparatus, rubber used as an elastic body has excellent resistance to chemicals and is lighter in weight than other materials. Therefore, deterioration of the first elastic piece through corrosion and the like can be suppressed and the apparatus can be made more lightweight.
The sixth aspect of the vibration isolating apparatus of the present invention is a vibration isolating apparatus according to any of the first to fourth aspects of the present invention, wherein the first elastic piece is a metal spring.
According to this vibration isolating apparatus, a metal spring used as an elastic body has excellent heat resistance. Therefore, even if used for long periods in a high temperature environment, deterioration of the first elastic piece cause by heat can be suppressed. Moreover, drops in performance due to reductions in the spring constant, changes in the free length, and the like caused by heat deterioration of the first elastic piece can be prevented.
The seventh aspect of the vibration isolating apparatus of the present invention is a vibration isolating apparatus comprising: a first elastic piece at one end of which is provided a first mounting member which is connected with a vibration generating portion; a second elastic piece at one end of which is provided a second mounting member connected with a vibration receiving portion, and at another end of which is connected the other end of the first elastic piece; and restraining means which, when operated, renders one of the first elastic piece and the second elastic piece incapable of elastic deformation.
The eighth aspect of the vibration isolating apparatus of the present invention is a vibration isolating apparatus according to the seventh aspect of the present invention in which the restraining means comprises an intermediate plate disposed between the first elastic piece and the second elastic piece, and attracting means provided in a fixed manner inside one of the first elastic piece and the second elastic piece, wherein the attracting means, when operated, attracts the intermediate plate or one of the first and second elastic pieces, each of which is provided in isolation from the attracting means.
The ninth aspect of the vibration isolating means of the present invention is a vibration isolating means according to the eighth aspect of the present invention, wherein the attracting means is fixed to the intermediate plate or to one of the first and second elastic pieces, and when operated, is supplied with drive current and driven.
The tenth aspect of the vibration isolating apparatus of the present invention is the vibration isolating apparatus according to the eighth or ninth aspects of the present invention, wherein the one of the first elastic piece and the second elastic piece inside which the attracting means is provided is a rubber elastic body or a metal spring.
The eleventh aspect of the vibration isolating apparatus of the present invention is the vibration isolating apparatus according to any of the eighth to tenth aspects of the present invention, wherein the distance separating the attracting means from either the intermediate plate or one of the first elastic piece and second elastic piece is greater than an amplitude of the idling vibration of the vehicle.
The twelfth aspect of the vibration isolating apparatus of the present invention is the vibration isolating apparatus according to any of the seventh to eleventh aspects of the present invention, further comprising a pressure receiving fluid compartment formed inside the second elastic piece, whose content volume is changed by elastic deformation of the second elastic piece, and a fluid sub-compartment whose content volume also changes and which is connected to the pressure receiving fluid compartment by a restricting passage.